DE1168885B - Process for the production of tetrachlorosuccinic acid or its anhydride - Google Patents

Description

Process for the production of tetrachlorosuccinic acid or its Anhydride It is a process for the production of free tetrachlorosuccinic acid known, in which dichloroacetic acid is reacted with diacetyl peroxide (USA.-Patent 2426 224). The known very explosive diacetyl peroxide must be used in this process be used in equimolecular amounts, thereby increasing the safety of the technical Implementation is greatly impaired. Tetrachlorosuccinic acid is also said to be used in the Oxidation of hexachlorobutadiene with oxygen by saponification of the initially formed Tetrachlorosuccinic acid dichloride is formed (US Pat. No. 2,807,579). at However, only very small amounts of tetrachlorosuccinic acid dichloride could be reworked for this process or tetrachiorhemstinic acid. Received by a different method an aqueous solution of tetrachlorosuccinic acid by the action of copper powder to dilute trichloroacetic acid (Journal of American Chemical Society, Vol. 44 [1922], pp. 636 to 640). Solid tetrachlorosuccinic acid could be produced by this process not yet isolated. Another way to make tetrachlorosuccinic acid lends itself to the chlorination of, -butyrolactone in an aqueous medium (German patent 1 085 516).

It is known that they are suitable for carrying out organic-chemical syntheses Anhydrides, namely cyclic anhydrides of dicarboxylic acids, in particular. One way of producing the anhydride of tetrachlorosuccinic acid is to this day Days not known.

It has now been found that, surprisingly, the anhydride of the Tetrachlorosuccinic acid is obtained by using the mixed anhydride of dichloroacetic acid and the trichloroacetic acid is dehydrochlorinated. The free tetrachlorosuccinic acid can be obtained if the reaction is carried out with the addition of a little water or the reaction product is saponified with a little water.

The invention relates to a process for the preparation of tetrachlorosuccinic acid or its anhydride, which is characterized in that the mixed anhydride of the die and trichloroacetic acid of the formula optionally in the presence of water, dehydrochlorinated. In the latter case, the water only needs to be added in the simple molecular amount. Under certain conditions, e.g. B. at temperatures above 1500 C, however, some water can also be formed by side reactions, so that in this case less than the theoretical amount of water is required for the formation of tetrachlorosuccinic acid.

The mixed anhydride of dichloroacetic acid and trichloroacetic acid is very easily accessible.

If you carry tri- or dichloroacetic acid or its sodium salts in di- or trichloroacetyl chloride, the result is a simple reaction mixed anhydride, for the production of which, however, protection is not claimed.

The dehydrochlorination, in the course of which tetrachlorosuccinic anhydride arises, is generally in the temperature range from 80 to 3500 C, in particular between 120 and 2000 C. Sometimes, especially when temperatures are maintained of the range given above, more or less large proportions of Dichloromaleic anhydride, apparently as a result of further dechlorination of Tetrachlorosuccinic anhydride.

Catalysts are advantageously present in the reaction. As catalysts are suitable, among other things, large-surface fabrics, such. B. silica, kieselguhr, Fuller's earth, clay, pumice powder, glass powder, activated carbon, and in particular metals the I. and II. subgroups or the II. main group of the periodic system or their salts, such as copper, zinc dust, copper (I) or copper (II) salts, magnesium, Calcium or zinc salts, barium salts, especially the sulfates and chlorides of these Metals, also tertiary amines, such as quinoline, tributylamine, collidine, isoquinoline, Salts of quaternary ammonium bases or salts of the tertiary amines mentioned and Dialkylamides, such as dimethylformamide, also iodine and iodine halides, like iodine chloride. The reaction can also be caused by the action of high-energy radiation, z. B. radioactive or ultraviolet radiation are favored.

The dehydrochlorination is preferably carried out in the liquid phase, although you can also work in the gas phase. In addition, the reaction can take place at atmospheric pressure, be carried out under reduced or increased pressure. One can do both continuously as well as working discontinuously. Inert diluents can also be used be present at the reaction. Suitable inert diluents are aliphatic, aromatic, cycloaliphatic and araliphatic hydrocarbons, e.g. B. at Room temperature liquid, natural or synthetic aliphatic hydrocarbons with boiling points up to 3000 C, diphenyl, decahydronaphthalene, tetrahydronaphthalene, Toluene, the various xylenes and cymene, cumene; Benzene, halogenated hydrocarbons, such as carbon tetrachloride, chloroform, methylene chloride, tetrachlorethylene, hexachloroethane, Monochlorobenzene, or p-dichlorobenzene, trichlorobenzene; Ketones, such as cyclohexanone, Acetylacetone; Ethers, such as ethylene glycol diethyl ether, diethylene glycol diethyl ether, Anisole; aromatic nitro hydrocarbons, such as nitrobenzene, or any mixtures such substances.

The reaction can also be carried out in such a way that one Di- or trichloroacetic acid chloride and those for the preparation of the mixed anhydride required chloroacetic acid together and the mixture of the two without the to wait for the actual formation of the anhydride, with or without the addition of a catalyst Subjects to dehydrochlorination.

Tetrachlorosuccinic acid and its anhydride are inexpensive intermediates for the production of plasticizers and polymers.

Example 1 147.5 g (1 mol) of technically pure dichloroacetyl chloride are melted at 1300 C in the course of 2 hours in 163.5 g (1 mol), technical pure trichloroacetic acid, which is provided in a cooler and exhaust pipe tl2-l round-bottomed flask, added dropwise with thorough stirring. This forms under Elimination of hydrogen chloride gas, the mixed anhydride of dichloroacetic acid and trichloroacetic acid. The internal temperature will increase over the course of another 5 hours gradually increased to 1500 C and heating after adding 3.1 g of fuller's earth (1 percent by weight, based on the total weight) continued for 100 hours.

The red-brown liquid that remains after cooling down (204 g) begins in the course of several hours with the separation of columnar Crystals partially crystallize. A raw spoil is obtained by suction of 72 g of tetrachlorosuccinic anhydride (30.30 / 0 of theory). These are through Squeezing or washing with some inert solvent, e.g. B.

Toluene, freed from small parts of still adhering mother liquor. Dissolving in petroleum ether gives tetrachlorosuccinic anhydride, which at about 155 to 1570 C (uncorrected) melts and has a chlorine content of 59.9ovo (59.60 / 0 is the chlorine content calculated for tetrachlorosuccinic anhydride).

The original filtrate is left to stand for one another part of tetrachlorosuccinic anhydride, which is separated in the same way and can be cleaned.

Tetrachlorosuccinic anhydride can be obtained just as well as by dissolving it from petroleum ether also by distillation or by a combination of dissolving and distillation clean.

Example 2 100 g of the mixed anhydride of die and trichloroacetic acid are with the addition of 0.1 weight percent fuller's earth as a catalyst in one Oil bath heated to 1800 ° C. for 30 hours with the gradual addition of 6.7 g of water heated. The weight loss due to the release of hydrogen chloride and loss of evaporation is 23.4 g. After cooling, most of the tetrachlorosuccinic acid obtained is present in crystallized form. It is made up of the mother liquor, which is also still free Contains tetrachlorosuccinic acid, separated by suction and recrystallized from hot xylene. The yield is 33.5 g = 38.6% of theory (chlorine content found 54, 65eo, calculated 55.5%) without taking into account the proportions dissolved in the mother liquor.

Example 3 In the manner described in Example 1, 737.5 g (5 mol) of technically pure dichloroacetyl chloride in 817.5 g (5 mol) of melted Trichloroacetic acid in the course of 3 hours at initially 1050 C with gradual Increase the temperature of the reaction mixture to 1300 C was added dropwise with stirring. The temperature is gradually increased to 1,400 over the course of a further 10 hours C and continues heating for about 14 hours, with the initially strong elimination of hydrogen chloride subsides again, away.

The mixed anhydride now formed from die and trichloroacetic acid a catalyst mixture of 13.7 g of activated fuller's earth (1 percent by weight, based on the original total weight) and 1.37 g of iodine were added and the reaction Continued for 60 hours with heating to 143 to 1440 C.

The reaction mixture, which has been cooled to about 500 ° C., is separated off The catalyst is removed by suction under an oil pump vacuum and the filtrate is cooled to avoid it the ingress of moisture under lock and key with the help of crushed ice away.

By sucking it off again, 346 g can be relatively pure Separate tetrachlorosuccinic anhydride.

720 g remain as mother liquor. From this, after again Add 13.7 g of fuller's earth and heat again to 143 bis for 60 hours At 1440 C, 283 g of tetrachlorosuccinic anhydride were again deposited.

The analytical numbers of the crude product dissolved with petroleum ether are: C1 59.350 / o, C 20.350 / o, H 0.20 / o; calcd Cl 59.66 O / o, C 20.17 O / o, H 00/0.

There is a further proportion of tetrachlorosuccinic anhydride dissolved in the mother liquor.

One can also proceed in such a way that the reaction according to the the first 60 hours of heating is interrupted, d. H. at a time when one partial conversion has taken place after separation of the tetrachlorosuccinic anhydride the mother liquor adds a new approach for further utilization and the implementation also in the following can only take place partially.

Claims (2)

Claims: 1. Process for the production of tetrachlorosuccinic acid or their anhydride, d a d u r c h characterized in that the mixed anhydride dichloroacetic acid and trichloroacetic acid, optionally in the presence of Water, at 80 to 3500 C, preferably at 120 to 2000 C, and preferably in Dehydrochlorinated in the presence of a catalyst. 2. The method according to claim 1, characterized in that as Catalyst large-surface substances, preferably bleaching earth and / or diatomaceous earth, used.